DNA as Genetic Material

Introduction

The genetic material in your cells is deoxyribonucleic acid or DNA. It was passed down to you from your parents and shaped your personality. Another significant milestone in molecular biology was the finding that DNA is a genetic material. 

In the early nineteenth century, it became commonly known that all living beings are made up of cells that arise solely from the growth and division of other cells. The advancement of the microscope then ushered in an age in which numerous biologists conducted extensive studies of the microscopic structure of cells. By 1885, a large body of indirect evidence suggested that chromosomes—dark-staining strands in the cell nucleus—carried the information for cell heredity. It was eventually discovered that chromosomes are made up of around half DNA and half protein.

DNA

A DNA molecule has two polynucleotide chains which are antiparallel to each other. Both the chains remain twisted in such a way that a double helix is formed. Both the chains remain united with the help of hydrogen bonds which are formed in between the nitrogen bases.Hydrogen bonds are formed between adenine (A) & thiamine (T) and cytosine (C) & guanine (G).  The two strands of DNA run antiparallel i.e. in opposite directions. One strand has phosphodiester linkage in 5’ → 3’ direction, while the other strand has phosphodiester in the reverse  3’→5’ direction.DNA is genetic material in eukaryotic,prokaryotic and some viruses.

DNA is the building block of life. The discovery of the DNA structure has resulted in significant advances in science, medicine, agriculture, and a variety of other sectors. As a result of the particular DNA structure, various types of mutations develop. Many methods, such as gene activation, methylation, and inhibition, have the ability of proteins to recognize well-defined sections of DNA and base cleavages of DNA, and one of the ways is the identification of local changes in secondary structure.

DNA as a Genetic Material

The various evidence of DNA being genetic material are as follows : It occurs in all the cells. It is capable of replication.DNA copies are precisely the same as the original DNA.

When DNA is duplicated, the new double-stranded DNA molecule has one parent strand (which serves as the replication template) and one freshly manufactured daughter strand. If there’s a base mismatch between the strands, as is common after replication, the cell can detect the proper base pair from the parent DNA strand and repair it. For example, if the parent strand comprises thymine and the daughter strand contains cytosine at one nucleotide location, the cell “knows” to correct the mismatch by following the steps in the parent strand. As a result, the cell will replace the cytosine in the daughter strand with adenosine. RNA cannot be repaired in this manner because it is single-stranded. 

There isn’t much of a distinction between DNA and RNA. DNA is double-stranded while RNA is single-stranded. DNA includes the sugar deoxyribose (a form of ribose that lacks one oxygen atom), whereas RNA contains the sugar ribose. Thymine is found in DNA, whereas uracil is found in RNA. 

Different Scientists like Frederick Griffith found out about the transformation in DNA in 1928, then in 1944, Scientists Avery, McCarty, and MacLeod established the ” transformation principle.”

Histone 

Histones are proteins that provide an important structure to DNA, allowing life to exist. These proteins act as spools around which the DNA coils. Unwound human chromosomal DNA, for example, would reach about 6 feet (2 meters). Without histones, DNA will not be arranged into chromosomes. Life as we know it would “cease to exist.” Histones also play a function in gene regulation. Histones, as a component of chromatin, aid in the regulation of “expression,” the process by which the coded information in genes is translated into operational structures in the cell.

Nonhistone

Nonhistone is defined as “the protein that remains in chromatin after the histones have been removed.” This little explanation does not credit the critical significance that nonhistones perform. Nonhistone proteins such as DNA polymerase, scaffold proteins, Polycomb, Heterochromatin Protein 1, and other motor proteins all play important roles in cell structure. Nonhistones, in reality, supply the scaffold structure of DNA and carry out a variety of structural and regulatory activities that allow life to exist.

Chromatin

The main protein components of chromatin are histones. Chromatin is defined as a “complex of nucleic acids (e.g., DNA or RNA) and proteins (histones) that condenses during cell division to create a chromosome.” Consider chromatin to be a vacuum package that permits a larger volume of garments to be neatly fit into a drawer. A single cell’s worth of DNA would unwind to an uncomfortable length of 1.8 meters without chromatin! In addition to packing, chromatin reinforces the DNA so that it does not lose structural integrity during cell division (either mitosis or meiosis).

• RNA AS A THE GENETIC MATERIAL IN VIRUS

DNA was thought to be the only carrier for storing genetic data. As a result, it came as a shock when it was revealed in 1971 that certain viruses change their genetic sequences from RNA to DNA. Nonetheless, most viruses eventually produce biomolecules in almost the same manner that elevated creatures do. According to the established system, during infections, the RNA code is first transcribed “back” to DNA, then to RNA, and finally to protein. Reverse transcriptase, a specialized polymerase, uses RNA as a template to create complementary and double-stranded DNA molecules.

• GENETIC MATERIAL OF PROKARYOTIC CELL 

Since there is no nuclear membrane in a prokaryotic cell, the nuclear area is poorly defined. The genetic substance found in prokaryotic cells is DNA. In prokaryotic cells, DNA is found in the nucleoid, which is located in the cell’s center. Because this type of cell lacks a nucleus, DNA is linked to the cell membrane and in direct contact with the cytoplasm.

Prokaryotic cells are the tiniest types of cells. Their genetic material is not kept in a lattice nucleus. It is instead kept in a nucleoid, which floats in the cytoplasm. Prokaryotic cells are typically smaller than eukaryotic cells, with an average diameter of 0.1–5.0 µm. Despite their small size, each cell contains a comprehensive chemical and biochemical machinery required for growth, replication, and energy acquisition and consumption. As a result, prokaryotic cells lack a proper nucleus. Prokaryotic cells’ genetic contents are exposed. They have a single circular chromosome that is devoid of histone proteins. Hence prokaryotic cells have non – historic double-stranded DNA. 

DNA is the genetic substance of bacteria and plasmids. Bacterial viruses (bacteriophages or phages) have genetic material in DNA or RNA. Replication and expression are the two most important processes of genetic material. The genetic material must replicate correctly so that progeny receives all of the parental organism’s distinct genetic determinants (the genotype). The observable traits (phenotype) of an organism are determined by the expression of certain genetic material under a specific set of growth conditions. Bacteria have few easily seen morphological or developmental traits, but they have a diverse range of metabolic capabilities and patterns of susceptibility to antimicrobial drugs or bacteriophages. These latter qualities are frequently chosen as the hereditary traits to be studied in bacterial genetics investigations.

Conclusion

In this article above, we have learned in detail about DNA as genetic material. Given how vital this structure is to our survival, it’s no surprise that its existence has influenced so many aspects of our life. We hope that by this time, you have a similar appreciation for what DNA is and what it can do, how it differs from RNA, and DNA fingerprinting.